In recent years, with the increase in integration of semiconductor elements and with the development of finer semiconductor elements, a wide variety of patterns has been formed on samples (e.g., semiconductor wafers) and the importance of evaluations and measurements of the shapes and the sizes of them has increased markedly. Regarding contact holes, which provide conduction between layers on semiconductor wafers in a multilayer construction, and deep grooves or the like formed between patterns, in particular, the hole diameters and the widths of the grooves become extremely small with miniaturization and the aspect ratio (the depth of holes or the like divided by the diameter (width) of holes or the like) tends to increase.
In order to perform inspection or measurement of bottom portions of such contact holes or the like, detection of secondary electrons excited by a bundle of primary electron rays (which may be referred to as “electron beam” hereinafter) is necessary; however, with the increase in aspect ratio, secondary electrons are more likely to impinge on the side wall of a hole and become extinct in the hole, making it difficult to inspect or measure the bottom of the hole. In Patent Literature 1, a technique to attach positive charge on a sample surface for forming an electric field for guiding electrons emitted from the bottom of a hole to the outside of the hole (referred to as “predosing” or “preliminary irradiation” in some case hereinafter) is proposed. More specifically, a technique to irradiate a sample region including a pattern of a hole or the like with a beam for charging a sample is described. In particular, a technique to separately perform predosing a certain number of times for forming a suitable surface electric field is described in Patent Literature 1.
In Patent Literature 2, a technique to perform interlaced scanning with a beam at the time of predosing so as to avoid a bias of charging in the area scanned with the beam is described. Interlaced scanning enables mitigation of the local bias of charging in the area scanned with the beam and guiding secondary electrons from holes to the outsides of the holes with improved efficiency.